If you’ve received an NGS report with the note “Please note: NGS results for sample [Sample ID] are indicative of low DNA concentration,” this article explains what that means, why it happens, and how it can affect your results.
Why does this happen?
Low DNA concentration can be caused by:
- Low microbial biomass in the original sample. This can occur in surface swabs or in high-purity systems where biological material is naturally minimal.
- Sample collection limitations, such as a small surface area, inadequate swabbing, or areas that were dry or recently cleaned.
This scenario is not unusual in:
- Corrosion failure analyses
- Tubing or pipeline wall sampling
- High-purity or low biomass environments
How does low DNA impact NGS and qPCR results?
Both testing methods can still offer useful insights from low DNA samples, but results must be interpreted carefully.
- NGS results: You may still detect microbial DNA, but overall diversity (unique taxa) and depth (number of reads) may be reduced. This means some organisms, especially those in low abundance, might not be captured reliably.
- qPCR results: qPCR can still detect microbes of interest, but if not enough of the microbial community was captured during sampling, qPCR may underestimate the true concentration of the target.
As a result, the reported values may not capture the actual microbial community present in the sampled environment.
Should I still trust the results?
Yes, even with low DNA, results can still provide a valuable snapshot of the microbial community present. This is especially true if key genera known to be involved in corrosion or biofouling are detected. These early signals are often enough to guide monitoring strategies and plan follow-up testing.
What should I do next?
We recommend:
- Using this data point as part of a longer-term monitoring plan
- Reassessing your sample collection technique if this occurs often
- Comparing across time points or locations to identify trends
Need Help or Want to Learn More?
Our team of experts is here to assist you with your microbiological monitoring needs. Whether you have questions, need technical support, or want to learn more about our Lab Services, contact LuminUltra® Support to get started.